Issue of flood in the cities
- Over 50 peple died in the wake of torrential rains in the third week of October in Hyderabad.
- This experience is not unique to the city of Hyderabad, five years ago Chennai saw a massive flood costing much damage and lives.
- Gurugram over the past few years comes to a complete standstill during the monsoon months.
- And for Mumbai, the monsoon has become synonymous with flooding and enormous damages.
Causes of frequent urban floods:
Natural:
- Meteorological Factors: Heavy rainfall, cyclonic storms and thunderstorms causes water to flow quickly through paved urban areas and impound in low lying areas.
- Hydrological Factors: Overbank flow channel networks, occurrence of high tides impeding the drainage in coastal cities.
- Climate Change: Climate change due to various anthropogenic events has led to extreme weather events.
Anthropological:
- Unplanned Urbanization: Unplanned Urbanization is the key cause of urban flooding. A major concern is blocking of natural drainage pathways through construction activity and encroachment on catchment areas, riverbeds and lakebeds.
- Destruction of lakes: A major issue in India cities. Lakes can store the excess water and regulate the flow of water. However, pollution of natural urban water bodies and converting them for development purposes has increased risk of floods.
- Unauthorised colonies and excess construction: Reduced infiltration due paving of surfaces which decreases ground absorption and increases the speed and amount of surface flow
- Poor Solid Waste Management System: Improper waste management system and clogging of storm-water drains because of silting, accumulation of non-biodegradable wastes and construction debris.
- Drainage System: Old and ill maintained drainage system is another factor making cities in India vulnerable to flooding.
- Irresponsible steps: Lack of attention to natural hydrological system and lack of flood control measures.
Impact of the devastation due to floods:
- On economy: Damage to infrastructure, roads and settlements, industrial production, basic supplies, post disaster rehabilitation difficulties etc.
- On human population and wildlife: Trauma, loss of life, injuries and disease outbreak, contamination of water etc.
- On environment: Loss of habitat, tree and forest cover, biodiversity loss and large scale greenery recovery failure.
- On transport and communication: Increased traffic congestion, disruption in rail services, disruption in communication- on telephone, internet cables causing massive public inconvenience.
What is to be done
1) Management of wetlands
- We neglect the issues of incremental land use change, particularly of those commons which provide us with necessary ecological support — wetlands.
- We need to start paying attention to the management of our wetlands by involving local communities.
- The risk is going to increase year after year with changing rainfall patterns and a problem of urban terrain which is incapable of absorbing, holding and discharging water.
2) Implementing the idea of sponge cities
- The idea of a sponge city is to make cities more permeable so as to hold and use the water which falls upon it.
- Sponge cities absorb the rain water, which is then naturally filtered by the soil and allowed to reach urban aquifers.
- This allows for the extraction of water from the ground through urban or peri-urban wells.
- This water can be treated easily and used for city water supply.
- In built form, this implies contiguous open green spaces, interconnected waterways, and channels and ponds across neighbourhoods that can naturally detain and filter water.
- It implies support for urban ecosystems, bio-diversity and newer cultural and recreational opportunities,
- These can all be delivered effectively through an urban mission along the lines of the Atal Mission for Rejuvenation and Urban Transformation (AMRUT), National Heritage City Development and Augmentation Yojana (HRIDAY) and Smart Cities Mission.
On a top priority, such a mission should address the following.
- 1) Wetland policy: In most of our lakes, the shallow ends, which often lie beyond the full tank level, have disappeared.
- These shallow ends are best characterised as wetlands.
- Regardless of ownership, land use on even this small scale needs to be regulated by development control.
- 2) Watershed management and emergency drainage plan is next.
- This should be clearly enunciated in policy and law.
- 3) Ban against terrain alteration is third.
- Lasting irreversible damage has been done to the city by builders, property owners, and public agencies by flattening terrain and altering drainage routes.
- 4) Use of porus material: Our cities are becoming increasingly impervious to water, not just because of increasing built up but also because of the nature of materials used.
- To improve the city’s capacity to absorb water, new porous materials and technologies must be encouraged or mandated across scales.
- Examples of these technologies are bioswales and retention systems, permeable material for roads and pavement, drainage systems which allow storm water to trickle into the ground, green roofs and harvesting systems in buildings.
Conclusion
We can learn to live with nature, we can regulate human conduct through the state and we can strategically design where we build. We need to urgently rebuild our cities such that they have the sponginess to absorb and release water without causing so much misery and so much damage to the most vulnerable of our citizens, as we have seen.
